JP2007131463A - Method of treating waste plastic containing carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably treat a waste plastic containing carbon fiber in a large amount in cement manufacturing equipment without causing reduction of the scavenging efficiency of a dust collector and without applying a special pretreatment for separating carbon fiber. <P>SOLUTION: In the method of treating a waste plastic containing a carbon fiber by supplying an exhaust gas which is generated by supplying the waste plastic containing a carbon fiber to a cement kiln for treating it by combustion, to a dust collecting apparatus for scavenging dust; the waste plastic containing a carbon fiber is pulverized to have an average particle size of 3 mm or smaller and supplied to a position where the internal temperature of the cement kiln is 1,200°C or higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention treats waste plastic containing carbon fiber without generating dust due to abnormal charging of the dust collector in a cement manufacturing process configured to supplement the dust in the cement kiln exhaust gas with a dust collector. Regarding the method.

In recent years, cement factories have been positioned as an important process for effectively using wastes such as plastics and sludge as fuel and raw materials for cement production. For example, Patent Document 1 describes a method in which waste FRP is introduced into a preheater in a cement manufacturing process and used as an auxiliary fuel.

However, when waste plastic containing carbon fiber is thrown into a kiln burner of a cement kiln and attempted to be treated, the dust collector for collecting the dust in the exhaust gas of the cement kiln causes a reduction in the dust collection efficiency. This causes the problem of dust generation. For this reason, when processing the waste plastic containing carbon fiber in a cement manufacturing apparatus, it was necessary to remove carbon fiber from waste plastic beforehand.
Japanese Patent Laid-Open No. 06-008247

The present invention does not cause a decrease in the collection efficiency, and carbon that can be stably processed in a large amount in a cement production apparatus without performing a special pretreatment of separating carbon fibers on waste plastics containing carbon fibers. It aims at providing the processing method of the waste plastic containing a fiber.

In order to solve the above problems, the present inventors have made extensive studies on the processing conditions such as the particle size and combustion temperature of waste plastic containing carbon fiber, and as a result, the carbon fiber is completely burned, and the electric dust collector The present inventors have completed the present invention by discovering knowledge that can prevent a reduction in collection efficiency due to charging abnormality.
That is, the present invention supplies carbon dioxide-containing waste plastic to a cement kiln and performs exhaust treatment to supply exhaust gas to a dust collector so as to collect the soot in the exhaust gas. In which the waste plastic containing carbon fiber is pulverized so as to have an average particle size of 3 mm or less and supplied to a position where the internal temperature of the cement kiln is 1200 ° C. or more. This is a method for treating waste plastics containing fibers.

According to the present invention, the waste plastic containing carbon fiber is stably processed in a large amount in a cement manufacturing apparatus without causing a decrease in the collection efficiency of the dust collector and without separating the carbon fiber. be able to. In addition, the quality of cement obtained by using waste plastics containing carbon fibers as part of the fuel is inferior to when cement plastics containing carbon fibers are not used.

The present invention will be described in detail with reference to FIG. FIG. 1 is a schematic view of a cement production apparatus for carrying out the present invention. First, the waste plastic containing carbon fiber used in the present invention will be described. The carbon fiber used in the present invention refers to a fiber made of graphite-like carbon and having excellent characteristics such as high strength and high rigidity. As an example of the carbon fiber, after performing a flameproofing treatment by heating polyacryl nitrile (PAN), pitch-based fiber or the like to 150 to 400 ° C. in an oxidizing atmosphere, 800 ° C. to 1400 in an inert atmosphere. 90 mass% or more of the whole obtained by heating to carbon and carbonizing is said.

To the waste plastic containing at least one kind of thermoplastic resin such as polyethylene, polypropylene and polystyrene, thermosetting resin such as phenol resin, ABS, nylon, etc. The coated, kneaded, melted, and welded materials are called waste plastics containing carbon fibers used in the present invention. Specific examples of the plastic containing carbon fiber used in the present invention include wastes of notebook computers and liquid crystal projectors that use a plastic compound containing carbon fiber.
Although the content rate of the carbon fiber in the waste plastic containing carbon fiber is not specifically limited, For example, 10-50 mass% is used preferably.

Waste plastic containing carbon fibers stored in a waste plastic tank 2 containing carbon fibers is supplied to the pulverizing apparatus 1 by a belt conveyor 3. Examples of the pulverizer include a vertical roller mill and a ball mill. A vertical roller mill is preferably used. Waste plastics containing carbon fibers are crushed in the pulverizer 1 to an average particle size of 3 mm or less. Here, the average particle diameter means an average particle diameter obtained by measuring the mass% on the sieve by passing the pulverized product through a sieve and calculating the diameter corresponding to 50% on the sieve.
Waste plastic containing carbon fibers crushed so as to have an average particle size of 3 mm or less is supplied to the dust collector 4 by air passing through the pulverizing apparatus. Waste plastic containing carbon fibers collected in the dust collector 4 is supplied to the kiln burner 21 and / or the waste plaburner 22 by compressed air.

Coal stored in the coal tank 18 is supplied to the crusher 14 by the belt conveyor 25. Examples of the pulverizer include a vertical roller mill and a ball mill. The pulverized coal, which is crushed coal, is supplied to the dust collector 16 by the air passing through the pulverizer. The pulverized coal collected in the dust collector 16 is supplied to the kiln burner 21 by compressed air.

  In the above description, the waste plastic containing carbon fiber and coal are individually pulverized and supplied to the rotary kiln 6, but the carbon fiber stored in the waste plastic tank 19 containing carbon fiber as shown in FIG. It is also possible to mix the waste plastics containing coal and coal and / or oil coke stored in the coal tank 18 and pulverize them in the pulverizer 14. Further, waste plastic containing carbon fiber and coal and / or oil coke can be independently supplied to the pulverizer 14 and mixed and pulverized. Thereby, compared with the case where the waste plastic containing a carbon fiber is grind | pulverized independently, abrasion of the component of a grinding | pulverization apparatus can be decreased. In addition, it is economically superior because an existing coal crusher can be used effectively without installing a new crusher.

The type of coal used in the present invention is not particularly limited, and any type of coal may be used. For example, the 1 type (s) or 2 or more types chosen from bituminous coal, unrelated coal, peat, lignite, and lignite can be used. The oil coke used in the present invention refers to a residue after further refining asphalt and pitch after petroleum refining.

  The supply ratio of waste plastic containing pulverized coal and carbon fiber supplied to the kiln burner 21 in the embodiment of FIGS. 1 and 2 is defined as waste containing carbon fiber when the total mass of waste plastic containing pulverized coal and carbon fiber is 100. The plastic is more than 0 and 10 or less, preferably 0.5 or more and 5 or less.

Waste plastic containing carbon fibers pulverized to an average particle size of 3 mm or less supplied to the waste platen 22 is fired in the rotary kiln 6. The type of the rotary kiln 6 is not particularly limited, and for example, a suspension preheater (SP) or a new suspension preheater (NSP) kiln can be applied. The temperature of the rotary kiln 6 is 950 ° C to 1500 ° C. In the present invention, it is necessary that the waste plastic containing carbon fiber is retained in the cement kiln at a temperature of 1200 ° C. or more and a residence time of 3 seconds or more.

Exhaust gas from the rotary kiln 6, kiln bottom 8, calcining furnace 9, and cyclone 23 is supplied to the humidity control tower 24. The exhaust gas conditioned by the humidity control tower 24 is supplied to the raw material crushing device 10 and heat exchanged with the cement raw material. The exhaust gas subjected to heat exchange is discharged from the chimney 12 after dust is removed in the electric dust collector 11.

Here, the electric dust collector 11 will be described with reference to FIG.
The electrostatic precipitator 11 passes the dust-containing gas 27 between the discharge electrode 30 to which a DC high voltage of about 80 kV is applied and the dust collection electrode 29, thereby applying electric charges to the particles in the gas by corona discharge, and charging particles. It adheres to the dust collecting electrode 29, removes particles in the gas, and discharges the purified gas 28. Dust collection by an electric dust collector uses corona discharge. The particles in the dust-containing gas 27 become a negatively charged body and move to the dust collecting electrode by Coulomb force. In this way, countless particles reach the dust collection electrode 29 one after another. These become large aggregates at the dust collection electrode 29 and fall out of the gas and separate from the gas and fall. In order to keep the dust collection efficiency constant, the electric dust collector constantly monitors the voltage with the voltmeter 32 and tries to keep the rectifier voltage constant. When carbon fiber with high conductivity is mixed in the dust-containing gas 26, the particles collected in the dust collecting electrode are locally highly conductive, and the electrolytic strength in the electrostatic precipitator 11 becomes extremely uneven. In addition, the indicated value of the voltmeter 32 is lowered, and the dust collection efficiency is lowered. In particular, when the voltmeter 32 indicated value decreases by 5 kV or more, the dust concentration meter 33 indicated value rises and dust is generated. An example of the dust concentration meter is a light transmission type.

[Example 1]
Waste plastic whose carbon fiber is coated on the surface of polyethylene by 10% by mass is preliminarily crushed to 30 mm or less by a rotary cutter type shear crusher, and then supplied to the center of a crushing table of a vertical roller mill with a separator through a supply pipe The waste plastic is pulverized by a plurality of rollers driven by a pulverizing table, discharged from the outer periphery of the pulverizing table, and the pulverized product is introduced into the separator by gas ejected from the lower periphery of the pulverizing table. The fine powder component is recovered as a product, and the coarse powder component is returned to the center of the grinding table and pulverized.
The pulverized products having an average particle diameter of 2 mm, 3 mm, 3.5 mm, and 4 mm were obtained by changing the number of rotations of the rotary blades installed in the separator and the amount of gas ejected from the lower periphery of the pulverization table. Specifically, in order to obtain 2 mm, the rotational speed of the rotating blades was increased to reduce the amount of gas to be ejected. On the other hand, in order to obtain a 4 mm pulverized product, the rotational speed of the rotating blades was decreased and the amount of gas to be ejected was increased. The average particle size was determined according to the following method. A sieve having a nominal mesh size of 9.5 mm, 4.75 mm, 1.18 mm, 600 μm, 300 μm, and 150 μm as defined in JIS Z 8801 is used. Item 7.2.2 of JIS R 5201 The sieve test was carried out according to the net sieve test procedure of After the sieving, the mass% on the sieve was measured, and the diameter corresponding to the mass on the sieve was calculated as the average particle diameter.

100 kg of the pulverized product per hour was put in the waste plate burner 22 of the NSP kiln shown in FIG. The supply amounts per hour of the cement raw material, the pulverized coal for the calciner and the pulverized coal for the kiln burner were 400 t, 13 t, and 13 t, respectively. The exhaust gas discharged from the preheater was 400 kNm3 / hour. In the electric dust collector 11, dust contained in the exhaust gas was collected. The amount of collected dust was 400 t per hour. The presence / absence of charging abnormality of the electrostatic precipitator during operation (whether the average value of fluctuation range per hour is set voltage ± 1 kV or less) was confirmed. The results are shown in Table 1. As a result, when the average particle size was 3 mm or less, no charging abnormality was observed in the electrostatic precipitator, and the dust collection efficiency was stabilized. Also, no change was observed in the dust concentration indicator value of the light transmission dust concentration meter installed at the exhaust gas outlet of the electrostatic precipitator. In addition, the quality of the cement clinker was comparable to that when no waste plastic was used.

[Comparative Example 1]
The waste plastic containing carbon fiber was burned under the same conditions as in Example 1 except that 100 kg of waste plastic containing carbon fiber per hour was added to the kiln bottom 8 in place of the waste plavaner 22 in Example 1. The results are shown in Table 1. As a result, each pulverized product was accompanied by a voltage drop of 5 kV or more.

[Comparative Example 2]
The waste plastic containing carbon fiber was combusted under the same conditions as in Example 1 except that 100 kg of waste plastic containing carbon fiber per hour was charged into the calcining furnace 9 instead of the waste plavaner 22 in Example 1. The results are shown in Table 1. As a result, each pulverized product was accompanied by a voltage drop of 10 kV or more.

[Example 2]
In the apparatus shown in FIG. 2, waste plastic in which 50% by mass of carbon fiber is kneaded with polyethylene preliminarily crushed to 70 mm or less by a rotary cutter type shear crusher is set to 0.02 per hour. 7 t was mixed and pulverized in the pulverizer 14. The average particle diameter of the waste plastic containing carbon fibers in the pulverized product obtained by mixing and pulverizing was determined according to the method shown below. 1 kg of the pulverized product was collected and 20 L of water was supplied. The waste plastic containing carbon fiber that floated on the water surface was scraped off and dried in a 40 ° C. incubator for one week. Thereafter, a sieve having a nominal mesh of 9.5 mm, 4.75 mm, 1.18 mm, 600 μm, 300 μm, and 150 μm, which is a sieve mesh specified in JIS Z 8801, was used, and the dried product was subjected to 7.2. Of JIS R 5201. A sieve test was carried out according to the mesh sieve test procedure of item 2. After the sieving, the mass% on the sieve was measured, and the diameter corresponding to the mass on the sieve was calculated as the average particle diameter. As a result, the average particle diameter was 3 mm. The pulverized product was supplied to the kiln burner 21 for combustion treatment. Except for the above, it was performed under the same conditions as in Example 1. As a result of confirming whether or not the electric dust collector 11 had a charging abnormality, no charging abnormality was observed and the dust collection efficiency was stabilized. Also, no change was observed in the dust concentration indicator value of the light transmission dust concentration meter installed at the exhaust gas outlet of the electrostatic precipitator. In addition, the quality of the cement clinker was comparable to that when no waste plastic was used.

The present invention can be used when waste plastic containing carbon fiber is used as a raw material or fuel for cement production.

It is the schematic of the cement manufacturing apparatus which implements this invention. It is the schematic of another cement manufacturing apparatus which implements this invention. It is the schematic showing the charge condition of the electric dust collector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crusher 2 Plastic tank containing carbon fiber 3 Belt conveyor 4 Dust collector 5 Fan 6 Rotary kiln 7 Front of kiln 8 Kiln bottom 9 Calciner 10 Raw material crusher 11 Electric dust collector 12 Chimney 13 Raw material supplied to cyclone Line 14 Crusher 15 Crusher 16 Dust collector 17 Dust collector 18 Coal tank 19 Tank for waste plastic containing carbon fiber 20 Tank for coal 21 Kiln burner 22 Waste plastic burner 23 Cyclone 24 Humidity control tower 25 Belt conveyor 26 Belt conveyor 27 Dust gas 28 Purified gas 29 Dust collecting electrode 30 Discharge electrode 31 Rectifier 32 Voltmeter 33 Dust concentration meter

Claims (3)

Waste plastic containing carbon fiber is supplied to a cement kiln and exhaust gas generated by performing a combustion process is supplied to a dust collector to collect soot dust in the exhaust gas. A waste plastic containing carbon fiber, characterized in that waste plastic containing carbon fiber is pulverized so as to have an average particle size of 3 mm or less and is supplied to a position where the internal temperature of the cement kiln is 1200 ° C. or higher. Processing method. The processing method of the waste plastic containing carbon fiber of Claim 1 which grind | pulverizes what mixed the waste plastic containing said carbon fiber, and coal and / or oil coke, and supplies it to the said cement kiln. The method for treating waste plastic containing carbon fiber according to claim 1 or 2, wherein the content of carbon fiber in the waste plastic containing carbon fiber is 10 to 50% by mass.

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